250-Watt Gold Line Power Amplifier
Glenayre Document Number: 9110.00160
THEORY OF OPERATION
Issue 1, Rev. C: 10/21/96
Page: 6-4
Copyright © 1996 Glenayre
Print Date: 12/17/96
After monitoring, the amplified RF output from the IPA is split in two by means of an RF
splitter, commonly known as a Wilkinson splitter. The two split RF signals are applied to
driver-1 (Q3) and driver-2 (Q4). The current drawn from each driver’s +25-volt power
source is monitored to determine the driver-1 and driver-2 current metering. The amplified
RF outputs from the two drivers are the driver board’s 40-watt RF outputs.
6.2.2
PA Board RF Flow
Each PA board amplifies a 40-watt RF input into a 150-watt RF output. Refer to
Figure 6-
3
. The RF input to the PA board is split into four signals by means of three Wilkinson split-
ters. Each RF signal drives a power amplifier, for a total of four amplifiers (Q1, Q2, Q3,
and Q4). Q1 and Q2 receive operating power from a 25-volt power source. The
current drawn by this source is monitored to determine the PA board’s A-pair current.
Likewise, the current drawn by Q3 and Q4 25-volt power source is monitored to
determine the PA board’s B-pair current.
The amplified RF outputs from the four power amplifiers are combined into one by means
of three Wilkinson combiners. The RF signal from the last Wilkinson combiner is
monitored for forward and reflected power levels. The power samples detected at this
location determine the PA board’s forward and reflected power metering. The combined
and monitored RF signal is the PA board’s 150-watt RF output.
6.2.3
Combiner Board RF Flow
The combiner board combines two 150-watt RF inputs into a single 275-watt RF output.
Refer to
Figure 6-3
. The two RF inputs are combined by a Wilkinson combiner. The
combined RF is monitored for forward power level. The power sample detected at this
location determines the total forward power metering. The combined and monitored signal
is the combiner board’s 275-watt RF output.
6.2.4
Isolator RF Flow
The isolator conducts its 275-watt RF input only in the forward direction, suppressing any
intermodulation or VSWR present at its RF output. Refer to
Figure 6-3
. The RF input is
applied through a circulator. The optional triple isolator RF input is applied through three
circulators.
Wilkinson Splitter/Combiner Theory
Wilkinson splitter and combiner networks are located in the RF signal path on the driv-
er board, PA boards, and combiner board. A waster resistor is located a precise dis-
tance from the signal junction. This resistor dissipates any out-of-phase imbalance or
amplifier imbalance that may exist between the RF signals being split or combined, re-
sulting in a more stable amplifier.
Circulator Theory
A circulator consists of several circular layers of copper, ferrite, and a magnetic materi-
al that biases the ferrite. The circulator has three inputs/outputs. The biased ferrite con-
ducts electricity only in one direction, outputting the signal applied at its previous
input. Each circulator provides 25 dB of isolation.
